An employee may not simultaneously receive a pension under more than one section of AS 39.35.095 - 39.35.680. However, benefits under AS 39.35.420(b), 39.35.430, 39.35.440 or 39.35.450 shall be paid in addition to the benefits or service credit a person is entitled to receive because of the person's own membership in the retirement plan. An employee may not (1) receive duplicate credit under this plan for the same period of service, (2) receive more than one year of service credit in the course of any calendar year, or (3) receive a benefit while accruing service credit under this plan, except as provided in this section.